Heat-recoverable polymeric articles are well known in the art. Such articles have found utility in the repair or protection of tubular conduits such as pipe or cable, and to seal generally cylindrical substrates such as cable splices, electrical connectors and the like. A number of patents have been issued dealing with this utility, examples of which include U.S. Pat. Nos. 2,207,692; 3,243,211; 3,297,819; and 3,415,287.
In some instances, heat-recoverable tubing has been utilized for some applications. In this case, however, a free end of the substrate is required over which the tubing can be positioned. Recently, wrap around heat-recoverable sleeves have been described as closure members, as for example in U.S. Pat. Nos. 3,379,218; 3,455,336; and 3,530,898, which typically contain an open longitudinal seam to allow placement of the sleeve over the substrate and thus eliminate the necessity for cutting the substrate to obtain thereby a free end over which a tubing could be placed.
Such heat-recoverable sleeves or closure members typically consist of a rectangular sheet, such as is disclosed in U.S. Pat. No. 3,847,721, among others, or a longitudinally slit tubing as is disclosed in the earlier referenced patents, which comprises a heat-recoverable plastic material having the property of elastic memory, the material typically having been rendered heat-recoverable by stretching same at an elevated temperature, followed by cooling while in the stretched shape, together with a means for closing the open longitudinal seam during subsequent shrinking. Furthermore, it is typical to coat the interior surface of the heat-recoverable sleeve with a heat-activatable adhesive, e.g., a hot melt adhesive, or a flowable mastic composition to ensure intimate contact or binding of the sleeve with the substrate surface. In addition, this heat-activated adhesive or sealant also functions to hermetically seal the cable at the location of the repair.
Several methods for joining an open longitudinal seam of a heat-recoverable wrap around sleeve during installation have been described in the art, as disclosed in the above-referenced patents. Such closure devices must be capable of maintaining the seam against the substantial shrinkage forces present during heat recovery of the sleeve. Mechanical closures have been utilized, and include such means as metal slip-on channels, as disclosed in U.S. Pat. No. 3,455,336; buttons, as disclosed in U.S. Pat. No. 3,379,218; threaded loops, as disclosed in U.S. Pat. No. 3,530,898; and embedded inserts, as is disclosed in U.S. Pat. No. 3,542,077. The use of such mechanical means for closure exhibit several disadvantages, however, e.g., the necessity of elaborate extrusion or molding processes for sleeve fabrication; the bulkiness and awkwardness of such mechanical closures; thermal stresses which may be generated during the heat-recovery stage, etc.
Recognizing these deficiencies, adhesive techniques were developed to hopefully eliminate same. Such adhesive systems capable of exhibiting sufficient strength to withstand the recovery forces of the heat-recoverable sleeve during recovery along the longitudinal seam include cyanoacrylates as disclosed in U.S. Pat. No. 3,959,052; silicone adhesives, as disclosed in U.S. Pat. No. 4,153,747; chloroprene-based contact adhesives, as disclosed in U.S. Pat. No. 3,770,556, and crosslinked hot-melt adhesives as described in U.S. Pat. No. 4,220,676. In addition, closures utilizing a pressure sensitive adhesive have been disclosed, wherein the adhesive is placed to two fixed edges of the sleeve, i.e., the fixed edges not being heat recoverable. These are disclosed in U.S. Pat. Nos. 4,153,747 and 4,268,559.
It can thus be seen that in the aforementioned references utilizing a hot melt adhesive patch to maintain closure, same limits the cable diameter size with which the heat recoverable sleeve can be utilized, because a cool portion must be maintained along the axis of the closure to in essence act as a brake to prevent the forces of contraction from shearing the hot melt adhesive under the patch and thus opening the closure.
In the systems utilizing pressure-sensitive adhesives, same is typically applied to each of two unstretched or fixed edges. Again, the use of such fixed edges is a limiting factor relative to cable diameter size, i.e. a rather large inventory of such sleeves are required in order to be utilized over a wide range of substrate diameters.
We have now determined that a heat-recoverable closure member can be provided having a crosslinked adhesive applied thereto. Such a closure member or sleeve allows adjustment to fit a wide variety of substrate diameters by simply trimming along the opposite edge of the sleeve, that which contains no pressure-sensitive adhesive thereon, to basically match the circumference of the substrate. Alternatively, adjustment can be undertaken by continuously wrapping the sleeve about the substrate to provide a loose fit. Such a sleeve obviously does not require precise alignment of one longitudinal seam along another, and application of the sleeve to the underlying substrate can be easily undertaken in the field by unskilled personnel.